Low-temperature halogen-free tin soldering paste and preparation method and application thereof

Abstract

The invention discloses low-temperature halogen-free soldering paste as well as a preparation method and application thereof. The low-temperature halogen-free soldering paste comprises tin-bismuth alloy, a carbon nano tube and soldering flux, the soldering flux comprises the following components in percentage by weight: 30-50% of film-forming resin, 5-15% of a rosin-based surfactant, 3-10% of an active agent, 2-8% of a thixotropic agent and the balance of a solvent. According to the low-temperature halogen-free tin soldering paste and the preparation method and application thereof, the compatibility between the carbon nano tube and the alloy is improved, a very excellent effect is achieved, the toughness and weldability of the tin soldering paste can be effectively improved, the voidage in a welding spot can be remarkably reduced, oxidation of the tin soldering paste in the storage and use process is prevented, and the service life of the tin soldering paste is prolonged. And the performance stability is maintained.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding materials, and in particular relates to a low-temperature halogen-free tin solder paste and a preparation method and application thereof. Background Art

[0002] As electronic information products advance toward ultra-large-scale integration and miniaturization, solder paste has become a crucial process material in surface mount technology (SMT). Traditional solder pastes commonly use SAC alloys (tin-silver-copper alloys), requiring temperatures typically exceeding 240°C. This can easily lead to device deformation during the soldering process of highly integrated microelectronic devices. Therefore, solder pastes using tin-bismuth alloys as low-temperature solders are currently more commonly used.

[0003] Because this type of solder paste contains a large amount of bismuth metal, the solder joints have low toughness, which in turn prevents electronic devices from meeting performance requirements. Carbon nanotubes, with their excellent mechanical, electrical, and thermal properties, are developing into an excellent reinforcement phase for traditional solder pastes. However, the nanometer size effect and fiber entanglement of carbon nanotubes make them difficult to disperse in solder pastes, and their poor compatibility with other ingredients prevents them from fully realizing their reinforcing properties in solder pastes.

[0004] Patent publication CN111151909A discloses a carbon nanotube-modified low-temperature solder and its preparation method. The low-temperature solder comprises nickel-plated carbon nanotubes, hydroxyl multi-walled carbon nanotubes, and a tin-bismuth alloy. The synergistic combination of the hydroxyl multi-walled carbon nanotubes and nickel-plated carbon nanotubes improves the compatibility between the carbon nanotubes and the alloy, resulting in excellent results. This solder can effectively enhance the toughness and weldability of the solder, providing reinforcement. While this patent enhances compatibility with tin alloys, allowing the carbon nanotubes to achieve a reinforcing and toughening effect, the process is relatively complex, the cost is high, and the product quality is inconsistent. Summary of the Invention

[0005] Based on the above technical problems, the present invention provides a low-temperature halogen-free tin solder paste and its preparation method and application, which improves the compatibility between carbon nanotubes and alloys, producing very excellent effects. It can not only effectively improve the toughness and weldability of the tin solder paste, but also significantly reduce the void rate in the solder joints, and prevent the solder paste from oxidation during storage and use, thereby maintaining its stable performance.

[0006] The present invention provides a low-temperature halogen-free tin solder paste comprising: a tin-bismuth alloy, carbon nanotubes and a flux;

[0007] The soldering flux comprises, by weight percentage, 30-50% of film-forming resin, 5-15% of rosin-based surfactant, 3-10% of activator, 2-8% of thixotropic agent, and the balance being solvent.

[0008] Preferably, the film-forming resin is at least one of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin or terpene resin.

[0009] Preferably, the rosin-based chelating agent is obtained by an addition reaction between rosin and 3-allyl-5,5-dimethylhydantoin.

[0010] Preferably, the rosin-based surfactant is obtained by chlorinating dehydroabietic acid, performing an amide condensation reaction with 3-dimethylaminopropylamine, and then performing a nucleophilic substitution reaction with 3-chloropropionic acid.

[0011] In the present invention, the structural formula of the rosin-based surfactant is as follows:

[0012]

[0013] In the present invention, the anionic groups contained in the above-mentioned rosin-based surfactant can have a coordination effect with the tin-bismuth alloy, and the cationic groups can adsorb the carbon nanotubes, thereby effectively promoting the compatibility of the carbon nanotubes and the tin-bismuth alloy, greatly improving the dispersibility of the carbon nanotubes in the solder paste, solving the problem of poor reinforcement effect of carbon nanotubes in the prior art, and improving the strength and toughness of the solder joints during soldering of the solder paste.

[0014] Preferably, the active agent is at least one of succinic acid, glutaric acid, adipic acid, azelaic acid, itaconic acid, salicylic acid or malic acid.

[0015] Preferably, the thixotropic agent is at least one of hydrogenated castor oil, aromatic polyamide, organic bentonite, polyethylene wax, ethylene bisstearamide, ethylene bislauramide or polyamide wax thixotropic agent; the solvent is at least one of ethylene glycol phenyl ether, tetraethylene glycol methyl ether, dipropylene glycol, polyethylene glycol 200, 2-ethyl-1,3-hexanediol, diethylene glycol hexyl ether, diethylene glycol dibutyl ether or tripropylene glycol butyl ether.

[0016] In the present invention, the synergistic effect of the activator and the thixotropic agent can make the solder paste more delicate, improve the high wettability of the solder paste, reduce welding defects and the number of tin balls. In addition, the solder paste provided by the present invention does not contain halogen and lead elements, is environmentally friendly, safe and reliable, and has less corrosion on the solder joints.

[0017] In the present invention, the solder paste further comprises: 1-5% of a rosin-based chelating agent;

[0018] The rosin-based chelating agent is obtained by carrying out a DA addition reaction on rosin and 3-allyl-5,5-dimethylhydantoin.

[0019] In the present invention, rosin includes levorotatory pimaric acid, so the representative structural formula of the rosin-based chelating agent is as follows:

[0020]

[0021] The carboxyl groups in the rosin-based chelating agent can, on the one hand, promote the removal of oxides and reduce the use of acidic activators, thereby achieving good wettability and solderability even in the absence of halogen activators. Furthermore, the dimethyl hydantoin contained in the rosin-based chelating agent has excellent chelating ability, which can chelate the metal elements on the surface of the tin-bismuth alloy, reducing the dissolution of the tin-bismuth alloy surface tension, promoting the fusion of solder powders, and reducing the solder void rate. Furthermore, the presence of the rosin base can improve the dispersibility of the tin-bismuth alloy tube in the solder paste and enhance the storage stability of the solder paste.

[0022] Preferably, the tin-bismuth alloy is Sn42Bi58, Sn64.5Bi35Cu0.5, Sn64.6Bi35Ag0.4, Sn42Bi57Ag1 or Sn42Bi57.6Ag0.4; and the carbon nanotube is a hydroxylated multi-walled carbon nanotube or a carboxylated multi-walled carbon nanotube.

[0023] Preferably, the tin-bismuth alloy accounts for 85-90 wt % in the solder paste, the flux accounts for 9-14 wt % in the solder paste, and the carbon nanotubes account for 0.05-1 wt % in the solder paste.

[0024] The present invention provides a method for preparing the above-mentioned low-temperature halogen-free tin solder paste, comprising the following steps:

[0025] After heating the solvent to 150-160°C, add the film-forming resin and stir to melt, then add the rosin-based surfactant and thixotropic agent and stir to melt, cool to 120-130°C, add the activator and stir to melt, and cool to obtain the flux;

[0026] The tin-bismuth alloy, carbon nanotubes and soldering flux are first stirred in a vacuum mixer for 5-10 minutes, then filled with nitrogen and stirred for 25-35 minutes, and then vacuumed and stirred for 5-10 minutes to obtain the low-temperature halogen-free tin solder paste.

[0027] The present invention also provides an application of the low-temperature halogen-free tin solder paste in electronic component packaging.

[0028] Compared with the prior art, the key of the present application is to use a specific rosin-based surfactant compound as a flux, and on this basis, a specific solvent, a film-forming resin, an active agent, a thixotropic agent and a rosin-based chelating agent are matched, so that the tin solder paste obtained not only has low temperature, is suitable for applications with more low temperature welding requirements, solves the problem that the medium and high temperature tin paste is not widely used, and can significantly reduce the void rate in the welding point. The low void rate directly improves the mechanical strength and electrical stability of the welding point, thereby providing higher connection reliability, and the addition of carbon nanotubes as an additive not only enhances the mechanical strength of the welding point, but also optimizes the thermal conductivity and electrical conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of the residue after the low-temperature halogen-free tin solder paste described in the embodiments of the present application is welded. DETAILED DESCRIPTION

[0030] In the following, the technical solutions are described in detail by specific embodiments, but it should be clear that these embodiments are used for illustration, but not to be interpreted as limiting the scope of the present application.

[0031] In the following examples, the hydrogenated rosin has a CAS number of 65997-06-0; the disproportionated rosin has a CAS number of 8050-09-7; the polymerized rosin has a CAS number of 65997-05-9; the hydrogenated castor oil has a CAS number of 8001-78-3; the aromatic polyamide has a CAS number of 5892-11-5; the ethylene bis-stearamide has a CAS number of 110-30-5; the diethylene glycol hexyl ether has a CAS number of 112-59-4; the tetraethylene glycol methyl ether has a CAS number of 23783-42-8; the diethylene glycol butyl ether has a CAS number of 203-961-6; and the triethylene glycol butyl ether has a CAS number of 143-22-6.

[0032] Example 1

[0033] The present application provides a low-temperature halogen-free tin solder paste, which comprises, by weight percentage: 86wt% of Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% of hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 13.9wt% of flux.

[0034] The flux comprises, by weight percentage: 30% of hydrogenated rosin, 10% of polymerized rosin, 10% of rosin-based surfactant, 2% of succinic acid, 5% of adipic acid, 3% of hydrogenated castor oil, 2% of ethylene bis-stearamide, and the balance of triethylene glycol butyl ether.

[0035] The rosin-based surfactant is synthesized by the following method: dehydroabietic acid is dissolved in dichloromethane, oxalyl chloride (40% by weight of the dehydroabietic acid) is added, the temperature is raised to 35°C, the mixture is stirred and reacted for 5 hours, and the mixture is distilled under reduced pressure to obtain dehydroabietic acid chloride; 3-dimethylaminopropylamine (80% by weight of the dehydroabietic acid) and triethylamine (1.2 times by weight of the dehydroabietic acid) are dissolved in dichloromethane, the dichloromethane solution containing the dehydroabietic acid chloride is slowly added dropwise at 0°C, the reaction is continued at room temperature for 5 hours after the addition is complete, and the mixture is heated to a pH of 12 with a hydrogen peroxide. The organic phase is washed five times with sodium chloride solution, the organic phase is collected and dried with anhydrous sodium sulfate, and after standing, the anhydrous sodium sulfate is removed by suction filtration, and the residual solvent is removed by distillation under reduced pressure, and the product is purified by silica gel column chromatography (the volume ratio of eluent methanol and ethyl acetate is 2:1) to obtain dehydroabietamide; dehydroabietamide and 3-chloropropionic acid are dissolved in ethanol, stirred and reacted at 90°C for 24 hours. After the reaction is completed, the residual solvent is removed by distillation under reduced pressure, and then recrystallized three times with an ethanol / acetone mixed solution to obtain the rosin-based surfactant. 1 H NMR (400MHz, CDCl3): δ7.03(m,2H),6.89(d,1H),6.93(s,1H),3.61(m,2H),3.36(s,6H),3.2 4-3.18(m,4H),2.90-2.78(m,5H),2.36-2.25(m,5H),1.85-1.35(m,12H),1.33-1.21(m,6H).

[0036] The preparation method of the low-temperature halogen-free tin solder paste comprises the following steps:

[0037] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt, and then rosin-based surfactant, hydrogenated castor oil and ethylene bisstearamide are added and stirred to melt. After cooling to 125°C, succinic acid and adipic acid are added and stirred to melt. After cooling, the flux is obtained.

[0038] The Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 8 minutes, then stirred for 30 minutes under nitrogen filling, and then stirred for 6 minutes under vacuum to obtain the low-temperature halogen-free tin solder paste.

[0039] Example 2

[0040] The present invention provides a low-temperature halogen-free tin solder paste, which comprises, by weight percentage: 85wt% of Sn42Bi58 alloy powder (average particle size of 40μm), 0.05wt% of carboxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 14.95wt% of flux paste;

[0041] The soldering flux comprises, by weight percentage, hydrogenated rosin 20%, disproportionated rosin 10%, rosin-based surfactant 5%, succinic acid 3%, glutaric acid 4%, adipic acid 3%, hydrogenated castor oil 1%, aromatic polyamide 1%, and the balance being diethylene glycol hexyl ether;

[0042] The rosin-based surfactant is synthesized by the method of Example 1.

[0043] The preparation method of the low-temperature halogen-free tin soldering paste comprises the following steps:

[0044] After the diethylene glycol hexyl ether is heated to 150 DEG C, the hydrogenated rosin and the disproportionated rosin are added and stirred to melt, then the rosin-based surfactant, the hydrogenated castor oil and the aromatic polyamide are added and stirred to melt, after being cooled to 120 DEG C, the succinic acid, the glutaric acid and the adipic acid are added and stirred to melt, and the soldering flux is obtained after cooling;

[0045] The Sn42Bi58 alloy powder, the carboxylated multi-walled carbon nanotube and the soldering flux are stirred in a vacuum stirrer for 5 min, then nitrogen is filled for stirring for 35 min, and then vacuum is applied for stirring for 5 min, to obtain the low-temperature halogen-free tin soldering paste.

[0046] Example 3

[0047] The present application provides a low-temperature halogen-free tin soldering paste, which comprises, by weight percentage, 90 wt% of Sn42Bi58 alloy powder (average particle size 40 μm), 0.5 wt% of hydroxylated multi-walled carbon nanotube (outer diameter 8-15 nm, length 0.5-2 μm) and 9.5 wt% of soldering flux.

[0048] The soldering flux comprises, by weight percentage, hydrogenated rosin 25%, polymerized rosin 25%, rosin-based surfactant 15%, succinic acid 1%, adipic acid 2%, hydrogenated castor oil 4%, ethylene bis-stearamide 4%, and the balance being tetraethylene glycol methyl ether and diethylene glycol butyl ether.

[0049] The rosin-based surfactant is synthesized by the method of Example 1.

[0050] The preparation method of the low-temperature halogen-free tin soldering paste comprises the following steps:

[0051] After the tetraethylene glycol methyl ether and the diethylene glycol butyl ether are heated to 160 DEG C, the hydrogenated rosin and the polymerized rosin are added and stirred to melt, then the rosin-based surfactant, the hydrogenated castor oil and the ethylene bis-stearamide are added and stirred to melt, after being cooled to 130 DEG C, the succinic acid and the adipic acid are added and stirred to melt, and the soldering flux is obtained after cooling.

[0052] The Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 10 minutes, then filled with nitrogen and stirred for 20 minutes, and then vacuumed and stirred for 10 minutes to obtain the low-temperature halogen-free tin solder paste.

[0053] Example 4

[0054] The present invention provides a low-temperature halogen-free tin solder paste, which comprises, by weight percentage: 86wt% of Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% of hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 13.9wt% of flux paste;

[0055] The soldering paste comprises, by weight percentage, 30% hydrogenated rosin, 10% polymerized rosin, 10% rosin-based surfactant, 3% rosin-based chelating agent, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bisstearamide, and the balance is triethylene glycol butyl ether;

[0056] The rosin-based surfactant was synthesized by the method described in Example 1. The rosin-based chelating agent was synthesized by heating rosin (acid value 180 mgKOH / g) to 230° C., then adding 3% by weight of hydroquinone and 20% by weight of rosin of 3-allyl-5,5-dimethylhydantoin. The mixture was kept warm under nitrogen for 4 hours, and then cooled and discharged to obtain the rosin-based chelating agent.

[0057] The preparation method of the low-temperature halogen-free tin solder paste comprises the following steps:

[0058] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt, and then rosin-based surfactant, rosin-based chelating agent, hydrogenated castor oil and ethylene bisstearamide are added and stirred to melt, and after cooling to 125°C, succinic acid and adipic acid are added and stirred to melt, and the flux is obtained after cooling;

[0059] The Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 8 minutes, then stirred for 30 minutes under nitrogen filling, and then stirred for 6 minutes under vacuum to obtain the low-temperature halogen-free tin solder paste.

[0060] Comparative Example 1

[0061] The present invention provides a low-temperature halogen-free tin solder paste, which comprises, by weight percentage: 86wt% of Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% of hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 13.9wt% of flux paste;

[0062] The soldering paste comprises, by weight percentage, 30% hydrogenated rosin, 10% polymerized rosin, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bisstearamide, and the balance is triethylene glycol butyl ether.

[0063] The preparation method of the low-temperature halogen-free tin solder paste comprises the following steps:

[0064] After heating triethylene glycol butyl ether to 155°C, add hydrogenated rosin and polymerized rosin and stir to melt, then add hydrogenated castor oil and ethylene bisstearamide and stir to melt, cool to 125°C, add succinic acid and adipic acid and stir to melt, and cool to obtain flux;

[0065] The Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 8 minutes, then stirred for 30 minutes under nitrogen filling, and then stirred for 6 minutes under vacuum to obtain the low-temperature halogen-free tin solder paste.

[0066] Comparative Example 2

[0067] The present invention provides a low-temperature halogen-free tin solder paste, which comprises, by weight percentage: 86wt% of Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% of hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 13.9wt% of flux paste;

[0068] The soldering paste comprises, by weight percentage, 30% hydrogenated rosin, 10% polymerized rosin, 10% betaine, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bisstearamide, and the balance is triethylene glycol butyl ether.

[0069] The preparation method of the low-temperature halogen-free tin solder paste comprises the following steps:

[0070] After heating triethylene glycol butyl ether to 155°C, add hydrogenated rosin and polymerized rosin and stir to melt, then add betaine, hydrogenated castor oil and ethylene bisstearamide and stir to melt, cool to 125°C, add succinic acid and adipic acid and stir to melt, and cool to obtain flux;

[0071] The Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 8 minutes, then stirred for 30 minutes under nitrogen filling, and then stirred for 6 minutes under vacuum to obtain the low-temperature halogen-free tin solder paste.

[0072] The solder paste was soldered using relevant standards, and the tensile strength of the solder joints was tested. X-ray equipment was used to detect the void rate after soldering, and the test was performed using conventional operating methods. The test results are shown in Table 1.

[0073] Tensile strength: tested according to GB 26511989 standard;

[0074] Drop test: The drop test is conducted according to the standard JESD22-B111, using the daisy chain BGA solder test link and 1500G drop conditions;

[0075] Storage stability: Place the solder paste in a sealed container at 25°C and 60% humidity and observe its appearance changes over 8 months.

[0076] Table 1 Performance test results of the low-temperature halogen-free tin solder pastes described in Examples and Comparative Examples

[0077]

[0078]

[0079] According to the results in Table 1, the low-temperature halogen-free tin solder paste provided by the present invention effectively improves the strength and toughness of the solder joints, and compared with the finished solder paste of corresponding specifications in the prior art, the post-soldering void rate is significantly reduced, and it is environmentally friendly and non-toxic, and can be adapted to the field of electronic packaging.

[0080] Figure 1 This is a schematic diagram of the residue after welding. As can be seen from the figure, the area around the solder joint is very smooth and there is no black residue at all.

[0081] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A low-temperature halogen-free tin solder paste, characterized in that: include: tin-bismuth alloy, carbon nanotubes, and flux; The soldering flux comprises, by weight percentage, 30-50% of film-forming resin, 5-15% of rosin-based surfactant, 3-10% of activator, 2-8% of thixotropic agent, and the balance being solvent.

2. The low voiding halogen-free tin solder paste according to claim 1, characterized in that: The film-forming resin is at least one of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin or terpene resin.

3. The low-temperature halogen-free tin solder paste according to claim 1 or 2, characterized in that: The rosin-based surfactant is obtained by subjecting dehydroabietic acid to acyl chloride, followed by an amide condensation reaction with 3-dimethylaminopropylamine, and then a nucleophilic substitution reaction with 3-chloropropionic acid.

4. The low-temperature halogen-free tin solder paste according to any one of claims 1 to 3, characterized in that: The active agent is at least one of succinic acid, glutaric acid, adipic acid, azelaic acid, itaconic acid, salicylic acid or malic acid.

5. The low-temperature halogen-free tin solder paste according to any one of claims 1 to 4, characterized in that: The thixotropic agent is at least one of hydrogenated castor oil, aromatic polyamide, organic bentonite, polyethylene wax, ethylene bisstearamide, ethylene bislauramide or polyamide wax thixotropic agent; the solvent is at least one of ethylene glycol phenyl ether, tetraethylene glycol methyl ether, dipropylene glycol, polyethylene glycol 200, 2-ethyl-1,3-hexanediol, diethylene glycol hexyl ether, diethylene glycol dibutyl ether or tripropylene glycol butyl ether.

6. The low-temperature halogen-free tin solder paste according to any one of claims 1 to 5, characterized in that: The solder paste further comprises: 1-5% of a rosin-based chelating agent; Preferably, the rosin-based chelating agent is obtained by subjecting rosin to a DA addition reaction with 3-allyl-5,5-dimethylhydantoin.

7. The low-temperature halogen-free tin solder paste according to any one of claims 1 to 6, characterized in that: The tin-bismuth alloy is Sn42Bi58, Sn64.5Bi35Cu0.5, Sn64.6Bi35Ag0.4, Sn42Bi57Ag1 or Sn42Bi57.6Ag0.4; the carbon nanotube is a hydroxylated multi-walled carbon nanotube or a carboxylated multi-walled carbon nanotube.

8. The low-temperature halogen-free tin solder paste according to any one of claims 1 to 7, characterized in that: The tin-bismuth alloy accounts for 85-90 wt % of the solder paste, the flux accounts for 9-14 wt % of the solder paste, and the carbon nanotubes account for 0.05-1 wt % of the solder paste.

9. A method for preparing the low-temperature halogen-free tin solder paste according to any one of claims 1 to 8, characterized in that: The following steps are involved: After heating the solvent to 150-160°C, add the film-forming resin and stir to melt, then add the rosin-based surfactant and thixotropic agent and stir to melt, cool to 120-130°C, add the activator and stir to melt, and cool to obtain the flux; The tin-bismuth alloy, carbon nanotubes and flux are first stirred in a vacuum mixer for 5-10 minutes, then filled with nitrogen and stirred for 25-35 minutes, and then vacuumed and stirred for 5-10 minutes to obtain the low-temperature halogen-free tin solder paste.

10. Use of the low-temperature halogen-free tin solder paste according to any one of claims 1 to 8 in electronic component packaging.

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